Remove the -F Terminal Groups on Ti3C2Tx by Reaction with Sodium Metal to Enhance Pseudocapacitance

MXenes, a new family of two-dimensional materials, have been recognized as promising candidates for supercapacitors because of their unique chemical and physical properties. It has been proven that the terminal groups on MXenes play a decisive role in the pseudocapacitance. In this study, we report a highly efficient strategy to remove the -F terminal groups of Ti3C2Tx. Our initial purpose was to explore the application of Ti3C2Tx in sodium-ion batteries, whereas we found that almost all the -F terminal groups on Ti3C2Tx could be eliminated by reaction with Na metal at high temperature, and abundant terminal -O was introduced after the subsequent washing step. The mechanism involved is clarified by combining systematical spectra analysis and density functional theory (DFT) calculations. In addition, the modulated Ti3C2Tx MXene shows an extraordinarily high specific capacitance of 521 F.g(-1) (at scan rate of 2 mV.s(-1)) or 578 F.g(-1) (at a discharge rate of 1 A.g(-1)) in 1. H2SO4, and 92% capacity could be retained even after 10000 cycles. This study should provide new insight into the surface chemistry of MXenes and facilitate its applications in a variety of fields.